Third, the characteristics of SMC materials
SMC used in axial magnetic field motors: The material is pressed from soft magnetic particles covered with an insulating film on the surface. The high-purity iron powder having good magnetic properties is mixed with the resin, and after treatment, a substance having high density and high strength and excellent compressibility is produced. The iron powder and lubricant mixture is first extruded, and during the extrusion process, stress is generated between the powders, which can be released by heat-treating the assembly at a sufficiently high temperature. The iron particles are electrically insulated from each other to ensure that SM (the material has a high electrical resistivity. The electrical resistivity, mechanical properties and magnetic properties of the SMC material depend on the size, density, thickness of the insulation, extrusion process and Heat treatment cycle. The characteristics of the sMc material can therefore be adjusted to suit the specific requirements of certain applications.
In general, the saturation magnetic density and relative magnetic permeability of SMC materials are lower than those of silicon steel sheets, as shown in Figure 2. The reason for the low magnetic permeability is that the magnetic flux in the SMC component must constantly pass through the non-magnetic insulation between the iron particles. The sMc material is used in motors because of its high electrical resistivity, which produces eddy current losses that are lower than those of silicon steel sheet materials. However, motors with SMC: materials have higher hysteresis losses. The total iron loss produced by the SMC material and the silicon steel sheet is shown in Figure 3. Another reason for the high loss of SMC is that the insulation between the iron particles on the surface of the sMc core is damaged, so that the eddy current loss on the surface is excessive. Therefore, the SMc stator core should be well pressed.
